Which equation is y = –3x2 – 12x – 2 rewritten in vertex form?

The vertex form is y = -3(x + 2)² + 10

Step-by-step explanation:

* Lets revise how to put the quadratic in the vertex form

- The general form of the quadratic is y = ax² + bx + c, where

 a , b , c are constants

# a is the coefficient of x²

# b is the coefficient of x

# c is the numerical term or the y-intercept

- The vertex form of the quadratic is a(x - h)² + k, where a, h , k

 are constants

# a is the coefficient of x²

# h is the x-coordinate of the vertex point of the quadratic

# k is the y-coordinate of the vertex point of the quadratic

- We can find h from a and b ⇒ h = -b/a

- We find k by substitute the value of h instead of x in the general form

 of the quadratic

 k = ah² + bh + c

* Now lets solve the problem

∵ y = -3x² - 12x - 2

∵ y = ax² + bx + c

∴ a = -3 , b = -12

∵ h = -b/2a

∴ h = -(-12)/2(-3) = 12/-6 = -2

- Lets find k

∴ k = -3(-2)² - 12(-2) - 2 = -3(4) + 24 - 2 = -12 + 24 - 2 = 10

* Lets writ the vertex form

∵ y = a(x - h)² + k

∵ a = -3 , h = -2 , k = 10

∴ y = -3(x - -2)² + 10

∴ y = -3(x + 2)² + 10

* The vertex form is y = -3(x + 2)² + 10

ANSWER

The vertex form is:

EXPLANATION

The given equation is:

We add and subtract the square of half the coefficient of x.

We simplify to get,

This is in the vertex form.

we have three similar triangles, because each has a right angle and shares an angle.   let's write the angles in order: opposite to short leg, long leg, hypotenuse.

cab similar to bad similar to cbd

or as ratios,

ca: ab: cb = ba: ad: bd = cb: bd: cd

we also know

ac = ad + cd

(ad+cd): ab: cb = ba: ad: bd = cb: bd: cd

(ad+cd)/cb=cb/cd

we have cb=6, ad=5 and seek x=cd.

we reject the negative root and conclude x=4

answer: 4